The Museum of the History of Science, Technology and Medicine at the University of Leeds

In the fourth of the Museum of HSTM’s public lectures, Clare O’Reilly and Juha Saatsi presented a truly integrated historical and philosophical account of the object which has become emblematic of scientific practice – the microscope. Below is an image of the late-nineteenth-century light microscope that was the object of our talk. It is held in the collections of the Museum of HSTM, along with a number of other excellent examples of nineteenth- and twentieth-century microscopy.

Seeing is believing. But what exactly should we believe on the basis of what is observed through scientific instruments like microscopes? Clare and Juha’s talk highlighted some of the scientific, historical and philosophical problems faced when making realist inferences from microscopic observations.

Clare, a PhD student with @hpsleeds, opened the lecture by introducing our large audience to some of the natural philosophers who documented the unseen microscopic world around them. Robert Hooke and Antony van Leeuwenhoek were two such irrepressibly curious people. Hooke’s 1665 Micrographia was a wonderfully detailed record of his observations, while Leeuwenhoek became known for his ‘little animals’. So extraordinary were their illustrations of magnified fleas, snowflakes and numerous other curios that contemporaries did not know whether to believe they were real.

‘Engraving of a flea’. Robert Hooke, Micrographia. Wellcome Library, London

The microscope’s reliability remained a subject of debate and uncertainty throughout the eighteenth century. This changed during the nineteenth century, however, as specimens could be cut more thinly and stained with dyes for more ready examination on glass slides. Indeed,the microscope had become such a powerful tool that it allowed biology to become the nineteenth-century science par excellence. A person’s skill now lay in preparing slides and ‘reading’ the images observed on those slides. The level of intuitiveness or inference required to ‘read’ slides meant that microscopy came to be considered an art form, rather than just a scientific procedure. By the 1930s Irene Manton, a plant cytologist at the University of Leeds, was becoming well known for her work with ultraviolet and, later, electron microscopes. Her electron microscope is still held in the collections of the Museum of HSTM.

Drawing upon Clare’s historical introduction, Juha introduced our audience to some of the key philosophical problems surrounding the limits of scientific knowledge and observation. Scientific instruments such as microscopes furnish us with knowledge that transcends what our senses could otherwise perceive of the natural world. But can this ever be an objective experience? What role does inference and observation play in microscopy?

There has been a growing reliance upon technologies that allow us to ‘see’ microscopic phenomena that were previously the subject of inference. The light microscope was one such example. However, it became subject to competing theories of empiricism and realism. Hooke’s optimism about microscopy – that there was nothing too small to escape inquiry, thereby opening up an entirely new visible world – was soon challenged by the empirical theories of his contemporaries. Empiricists believed that scientific instruments did not, as Hooke hypothesised, reveal what existed behind observable phenomena, but instead created entirely new sets of phenomena to be observed and interpreted independently.

Empiricists, such as John Locke, questioned whether phenomena observed under the microscope could be used reliably to understand the natural world. For example, could the ‘nature’ of blood be understood through microscopic examination? Its colour and consistency changed so dramatically under the microscope that Locke believed it impossible to observe its natural mechanisms, which correlated microscope images with what was observable to the naked eye. Locke was not simply highlighting the mechanical limitations of the apparatus. He was philosophically challenging whether microscopes could ever reveal true microstructures, rather than simply an impression open to inference and interpretation.

Today, however, many philosophers have adopted the middle ground between realism and empiricism, and Juha concluded the lecture with a brief discussion of this position. ‘Moderate realism’ posits that we can learn to see with microscopes, but not through them. Microscopes facilitate interaction with the natural world, but do not provide a more high-resolution version of reality. It is instead a continuum of vision.

If you would like to see more commentary and images from this and other lectures in the series, follow the Twitter hashtag #hpsin20.